1. The Field of the Invention
The present invention relates generally to electrical connectors. More particularly, embodiments of the present invention relate to an improved electrical connector that is electromagnetically shielded and provides for a secure, low-profile physical/electrical connection with a mating media plug.
2. The Relevant Technology
The demand for personal computers and related equipment continues to expand due to a number of factors. One important factor is in that the prices of computers continues to decline. Another factor is the expansion and development of the Internet and related network communications. More and more commercial and non-commercial enterprises are conducting business via the Internet and consumers need personal computers to gain access to the products and information that are available on the Internet.
In addition to being more affordable, advances in computer application software, operating systems and communications software has fueled the development of computers having greater processing speeds and capacities. At the same time, the pressure to at least maintain, or preferably reduce, the physical size of the computer has increased as well. Accordingly, downsizing and miniaturization of computer components is an issue of great importance in the industry.
In an effort to reduce the form factor of the typical personal computer, and yet expand the capabilities of that computer, manufacturers began to develop miniature portable expansion devices having smaller sizes, such as add-on memory cards and modems. The typical expansion device was designed to plug into a port or socket on the main computer; thus the expansion device served to expand the capability of the computer without significantly increasing the size of the computer's physical envelope.
While the development of portable expansion devices represented a significant advance in the capabilities of personal computers, one drawback of many of the devices was that they were designed to fit only one manufacturer's computer, and thus were not interchangeable between platforms. The industry recognized that standardization of these devices would, among other things, greatly increase the demand for them. To this end, several manufacturers collaborated to form the Personal Computer Memory Card International Association (PCMCIA). This body developed and promulgated standards for the physical design, dimensions, and electrical interface of expansion devices. Now, many computers being manufactured, especially those having a reduced size, are adapted to accommodate these standards.
PCMCIA cards have become very popular because of their relatively small size, interchangeability, and capability. However, as a result of the relentless drive for smaller and more capable computers, the industry has developed a new generation of expansion devices with an even smaller form factor than that of PCMCIA cards. The new expansion devices, or cards, are sometimes referred to as "compact flash" or "miniature flash" cards.
Some examples of the new devices include compact flash memory cards, which are solid state storage devices that may have a storage capacity as high as 40MB; modems; and local area network (LAN) cards. The new compact devices have a very small "form factor" or physical size. A typical compact flash card uses about 1550 mm.sup.2 (36 mm long.times.43 mm wide) of space on a circuit board. In contrast, a typical card built to PCMCIA standards uses almost three times as much circuit board space, or about 4644 mm.sup.2 (86 mm long.times.54 mm wide).
Clearly, the compact flash form factor represents an important advancement in the art. However, the smaller form factor has also created some new problems that must be overcome in order that the maximum performance and reliability of the compact flash cards may be realized. Certain of these problems are particularly acute in those compact flash LAN cards that use a 4 pin input/output (I/O) connector. Some of the problems flowing from the use of the new form factor concern the construction and composition of the compact flash media card. Other problems concern the physical and electrical interfaces between the compact flash card and the various types of media cables used to carry media between the flash card and other devices.
One of the shortcomings common in current compact flash card designs concerns the harmful electromagnetic radiation produced by the card. Electromagnetic radiation is a natural consequence of current flow through the electrical circuits on the card. Unchecked, electromagnetic radiation can interfere with and disrupt the operation of electrical and electronic circuits in the host device. The interference resulting from electromagnetic radiation is commonly known as electromagnetic interference (EMI). Because electromagnetic radiation is a natural consequence of current flow, it cannot practically be prevented. Instead, emissions of the electromagnetic radiation must be controlled in order to prevent harmful EMI from resulting.
It is generally acknowledged that metal or metallic structures, if properly located and grounded, can be effective in controlling harmful electromagnetic radiation. Metals are effective in this regard because they generally have a low characteristic impedance which has the desirable characteristic of reflecting the high impedance electromagnetic radiation typically emitted by computers and related devices. By reflecting the electromagnetic radiation away from vulnerable circuits or devices, the metal thereby acts as a protective shield. Materials which can absorb electromagnetic radiation would be effective as well. However, typical compact flash cards are housed in a bay or enclosure, inside the host device, that is constructed of plastic or the like. The non-metallic enclosures are largely ineffectual in reflecting the electromagnetic radiation produced by the card. Furthermore, even though many compact flash cards employ metal covers, those covers are nevertheless inadequate to reflect electromagnetic radiation. This is due to the fact that effective EMI control cannot be achieved unless the metal covers typically utilized in compact flash cards are electrically bonded together and grounded. Since the metal covers of typical compact flash cards are not bonded and grounded, those covers are generally of little use in preventing PCB-generated EMI.
While it is clear that there are unresolved concerns regarding EMI and the construction of the compact flash cards, EMI problems are not limited solely to the card itself. As suggested earlier, some of the problems flowing from the new compact flash form factor relate to the physical/electrical interface used to connect a media cable to the card.
In particular, the current flowing through the media cable and the physical/electrical interface, or I/O connector, generates electromagnetic radiation which, in turn, causes harmful EMI. Many of the connectors currently in use with the compact flash card, including the 4 pin connectors, lack any device or means to reflect or absorb the electromagnetic radiation produced by the connector. Thus, when a media plug at the end of the media cable is inserted into the compact flash card connector, the unchecked electromagnetic radiation that is produced as a result of current flow through the connector, acts to interfere with the operation of electrical and electronic components inside the compact flash card and in the host device.
Not only are the typical compact flash card I/O connector designs ineffectual in preventing harmful EMI, those connectors suffer from other shortcomings as well. A significant problem concerns the structural configuration of the typical connector. In particular, the physical shape of the receiving portion, or aperture, of the connector, i.e., the portion that receives a mating media plug, is such that the connector can readily accommodate modular plugs. For instance, the connector may be capable of receiving a modular plug from a telephone line or a network line. This can give rise to a significant problem if the compact flash card comprises a LAN card, for instance, which is inadvertently connected to a telephone line. In particular, the telephone ring voltage that is applied to a modem line could damage the electronics on a LAN card. Thus, because a user may not always be able to readily ascertain whether a particular connector is a modem card connector or a LAN card connector, it would be relatively easy for a user to inadvertently plug a modem cord into the connector typically used with compact flash LAN cards, and thereby expose the LAN card to harmful telephone ring voltages.
Finally, in addition to their structural deficiencies and the EMI problems that they present, the typical compact flash card I/O connector suffers from an insubstantial and ineffectual mechanical interface with media plugs. Again, this problem results from the small physical size of the card or peripheral, which also limits the size and functionality of any connector that is used. In particular, larger connector schemes provide a more robust and functional retention scheme for maintaining a connection. Moreover, the connectors also provide a user with a tactile "feedback" that indicates when a plug has been satisfactorily received by a connector. In contrast, miniaturized connector schemes provide less physical space in which to provide a satisfactory retention mechanism and any sort of tactile feedback.
For example, a significant problem with existing compact flash I/O connector retention mechanisms is that the contact area between the retaining portion of the receptacle and the retained portion of the plug, respectively, is relatively small. Accordingly, the forces required to insert and withdraw the mating media plug are correspondingly small. Small insertion and withdrawal forces are problematic at least partly because they fail to provide the audible and tactile feedback necessary to indicate to the user that the media plug has engaged the receptacle portion of the connector. Indeed, the feedback provided by typical mechanisms is oftentimes so minimal--as low as 1 to 2 pounds--that the user cannot be certain that latching has occurred. Finally, an implicit and undesirable consequence of small insertion and withdrawal forces is that the media plug is likely to be inadvertently removed from the connector even during normal use.
In view of the foregoing problems with miniaturized peripherals, such as compact flash cards, and their associated I/O connectors, what is needed is an improved shielded I/O connector that can be used with compact flash card-sized devices, such as LAN cards and modem cards. Specifically, the connector should be able to reflect and/or absorb the electromagnetic radiation produced by the connector when current flows through the connector. Further, the connector should be grounded and should be capable of physically and electrically connecting the top and bottom covers of the housing of a compact flash card so that the covers can function effectively as a shield against the electromagnetic radiation emitted by the PCB. Additionally, the connector should be configured in such a way as to ensure that a particular compact flash card is only connectible with media plugs, cables, devices, and the like, that are electrically compatible therewith. Also, the connector should provide a tactile and audible feedback that indicates to the user that the mating media plug is properly received and seated within the connector. Moreover, the retention force exerted by the connector on the received plug should resist at least some inadvertent withdrawals of the plug during normal use.